1. Field of the Invention
The present invention relates to a production method of a thermally expandable base material for a vehicle interior and a production method of a base material for a vehicle interior using the same.
2. Discussion of the Background
Conventionally, a base material for a vehicle interior material is used which is produced by depositing a mixture of an inorganic fiber and a resin fiber, needling the deposit to fabricate a mat, heating the mat at a temperature at which the resin fiber is melt, hot-pressing the mat, and then cold-pressing the mat to mold. The base material has good thermal dimensional stability, and thus the rate of the thermal dimensional change is low. For the purpose of obtaining a vehicle interior material having high rigidity, however, the base material must have a high basis weight, and thus cannot meet the recent demand for the reduction of vehicle weight.
In order to solve the above problem, proposed is a base material for vehicle interior in which a thermally expandable microcapsule is incorporated into a mat obtained depositing a mixture of an inorganic fiber and a resin fiber and/or resin powder. The weight of the base material can be readily reduced since the thermally expandable microcapsule is expanded during secondary molding. In addition, the secondary molded product has a sufficient thickness and high rigidity. Such base material may be produced by, for example, incorporating a thermoplastic resin binder and a foamable microsphere into a needled fiber felt which is composed mainly of a glass fiber while being dispersed, and then blowing (for example, in JP-A H02-45135). Additionally, a production method of an expanded article is known in which a reinforced fiber, a thermally expandable powder and the like are dispersed in a specific aqueous medium to prepare a bubble solution, and the bubble solution is subjected to forming into a web, the web is heated, compressed, and cooled to fabricate a stampable sheet, the stampable sheet is heated to expand the thermally expandable powder, molded, and then cooled (for example, in JP-A 2006-342437).